In the field of marine science observation, observing and researching on spatial and temporal distribution rules of marine geomagnetism is one of basic contents for marine science observation. A high-sensitivity IM is an essential tool for this scientific activity. Information of variation in a natural magnetic field in a range of 0.1 mHz-100 Hz may be accurately acquired by using the high-sensitivity IM. The information in the band is of very important reference value for research on geosciences such as a submarine geological structure, plate tectonic movement or the like.
With the rise of deep water oil and gas exploration, the marine electromagnetic method has become one of the important means for marine oil and gas exploration. The practice of marine oil and gas exploration at home and abroad shows that the marine electromagnetic method greatly improves the drilling success rate and effectively reduces the cost of marine oil exploration and exploitation by identifying resistivity of target geological bodies. Almost all marine electromagnetic instruments measure a magnetic field component by using an IM, for example, marine electromagnetic instruments from corporations such as the SIO Research Institute, Schlumberger in the United States or the like.
Thus, no matter whether in the field of marine science observation or in the field of marine resources and energy sources, IMs are an indispensable core technology, which directly restricts the development of marine electromagnetic instruments. Normally, a sensitivity of an IM is in a range of 10−4nT/√Hz-10−3nT/√Hz (at 1 Hz). The existing IMs comprise the MTC-80 magnetometer and MTC-50 magnetometer from the PHOENIX Geophysics Limited corporation in Canada, the MFS-06(e) magnetometer and MFS-07 magnetometer from the Metronix Geophysics Corporation in German or the like.
These magnetometers have a length in a range of 1 m-1.4 m, a diameter of about 10 cm, and a mass in a range of 8 kg-12 kg. In the process of marine surveillance, three magnetometers are required to be sealed respectively by a long cylindrical pressure cabin and dipped into the bottom of the sea, and a signal is transmitted to a receiver inside an instrument housing via a waterproof cable. The entire IM has a volume exceeding 1 m3, and a weight greater than 400 kg. Further, 4-5 deep sea instrument housings are needed to ensure enough buoyancy. Disadvantageously, the excessively large volume and excessively high cost of the magnetometer have brought great challenges to the exploration operation. However, if the volume of the magnetometer is reduced, the sensitivity may be correspondingly reduced, and an equivalent input noise may be increased, which cannot meet the requirements for the measurement accuracy in the field of marine science observation or in field of marine resources and energy sources.